The present invention relates to a seat belt buckle. More particularly, the invention relates to a seat belt buckle with a swivel latch mounted in a load bearing frame and which engages in its locked position a latching edge of an insert tongue. In a buckle of this type a locking member is shiftably mounted on the frame transversely to the swivel direction of the swivel latch between an opening position, in which it releases the swivel latch, and a locking position in which it blocks the swivel latch in its engaging position. A release button is also mounted on the frame. By actuation of the release button the locking member is shifted to the opening position. A helical pressure spring has one end supported by the swivel latch and another end supported by the locking member. The spring is held by a spring receptacle which is defined by two ridges of the frame and which surrounds a spigot on the locking member.
Buckles of this kind for seat belts have already been in use for many years due to their rugged and simple mechanical arrangement, their high reliability and low actuating forces required even when under load.
In the more or less fully automated assembly of this buckle malassembly may result by the pressure spring inserted between the swivel latch and the locking member being installed so that although being supported by the locking member it fails to register fully home as required in its receptacle. This malassembly results in a spring force deviating only slightly from the prescribed value and may thus remain unnoticed.